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eliminate enter_alloc -- use kalloc for everything
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Robert Morris committed Sep 13, 2011
1 parent 7e7cb10 commit c092540
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Showing 4 changed files with 52 additions and 50 deletions.
7 changes: 3 additions & 4 deletions defs.h
View file
Expand Up @@ -62,11 +62,10 @@ extern uchar ioapicid;
void ioapicinit(void);

// kalloc.c
char* enter_alloc(void);
char* kalloc(void);
void kfree(char*);
void kinit(void);
uint detect_memory(void);
void kinit1(void*, void*);
void kinit2(void*, void*);

// kbd.c
void kbdintr(void);
Expand Down Expand Up @@ -165,7 +164,7 @@ void uartputc(int);
void seginit(void);
void kvmalloc(void);
void vmenable(void);
pde_t* setupkvm(char* (*alloc)());
pde_t* setupkvm();
char* uva2ka(pde_t*, char*);
int allocuvm(pde_t*, uint, uint);
int deallocuvm(pde_t*, uint, uint);
Expand Down
55 changes: 31 additions & 24 deletions kalloc.c
View file
Expand Up @@ -9,42 +9,45 @@
#include "mmu.h"
#include "spinlock.h"

void freerange(void *vstart, void *vend);
extern char end[]; // first address after kernel loaded from ELF file

struct run {
struct run *next;
};

struct {
struct spinlock lock;
int use_lock;
struct run *freelist;
} kmem;

extern char end[]; // first address after kernel loaded from ELF file
static char *newend;

// A simple page allocator to get off the ground during entry
char *
enter_alloc(void)
// Initialization happens in two phases.
// 1. main() calls kinit1() while still using entrypgdir to place just
// the pages mapped by entrypgdir on free list.
// 2. main() calls kinit2() with the rest of the physical pages
// after installing a full page table that maps them on all cores.
void
kinit1(void *vstart, void *vend)
{
if (newend == 0)
newend = end;
initlock(&kmem.lock, "kmem");
kmem.use_lock = 0;
freerange(vstart, vend);
}

if ((uint) newend >= KERNBASE + 0x400000)
panic("only first 4Mbyte are mapped during entry");
void *p = (void*)PGROUNDUP((uint)newend);
memset(p, 0, PGSIZE);
newend = newend + PGSIZE;
return p;
void
kinit2(void *vstart, void *vend)
{
freerange(vstart, vend);
kmem.use_lock = 1;
}

// Initialize free list of physical pages.
void
kinit(void)
freerange(void *vstart, void *vend)
{
char *p;

initlock(&kmem.lock, "kmem");
p = (char*)PGROUNDUP((uint)newend);
for(; p + PGSIZE <= (char*)p2v(PHYSTOP); p += PGSIZE)
p = (char*)PGROUNDUP((uint)vstart);
for(; p + PGSIZE <= (char*)vend; p += PGSIZE)
kfree(p);
}

Expand All @@ -64,11 +67,13 @@ kfree(char *v)
// Fill with junk to catch dangling refs.
memset(v, 1, PGSIZE);

acquire(&kmem.lock);
if(kmem.use_lock)
acquire(&kmem.lock);
r = (struct run*)v;
r->next = kmem.freelist;
kmem.freelist = r;
release(&kmem.lock);
if(kmem.use_lock)
release(&kmem.lock);
}

// Allocate one 4096-byte page of physical memory.
Expand All @@ -79,11 +84,13 @@ kalloc(void)
{
struct run *r;

acquire(&kmem.lock);
if(kmem.use_lock)
acquire(&kmem.lock);
r = kmem.freelist;
if(r)
kmem.freelist = r->next;
release(&kmem.lock);
if(kmem.use_lock)
release(&kmem.lock);
return (char*)r;
}

15 changes: 6 additions & 9 deletions main.c
View file
Expand Up @@ -9,13 +9,15 @@
static void startothers(void);
static void mpmain(void) __attribute__((noreturn));
extern pde_t *kpgdir;
extern char end[]; // first address after kernel loaded from ELF file

// Bootstrap processor starts running C code here.
// Allocate a real stack and switch to it, first
// doing some setup required for memory allocator to work.
int
main(void)
{
kinit1(end, P2V(4*1024*1024)); // phys page allocator
kvmalloc(); // kernel page table
mpinit(); // collect info about this machine
lapicinit(mpbcpu());
Expand All @@ -33,9 +35,9 @@ main(void)
ideinit(); // disk
if(!ismp)
timerinit(); // uniprocessor timer
startothers(); // start other processors (must come before kinit)
kinit(); // initialize memory allocator
userinit(); // first user process (must come after kinit)
startothers(); // start other processors
kinit2(P2V(4*1024*1024), P2V(PHYSTOP)); // must come after startothers()
userinit(); // first user process
// Finish setting up this processor in mpmain.
mpmain();
}
Expand Down Expand Up @@ -84,12 +86,7 @@ startothers(void)
// Tell entryother.S what stack to use, where to enter, and what
// pgdir to use. We cannot use kpgdir yet, because the AP processor
// is running in low memory, so we use entrypgdir for the APs too.
// kalloc can return addresses above 4Mbyte (the machine may have
// much more physical memory than 4Mbyte), which aren't mapped by
// entrypgdir, so we must allocate a stack using enter_alloc();
// this introduces the constraint that xv6 cannot use kalloc until
// after these last enter_alloc invocations.
stack = enter_alloc();
stack = kalloc();
*(void**)(code-4) = stack + KSTACKSIZE;
*(void**)(code-8) = mpenter;
*(int**)(code-12) = (void *) v2p(entrypgdir);
Expand Down
25 changes: 12 additions & 13 deletions vm.c
View file
Expand Up @@ -43,7 +43,7 @@ seginit(void)
// that corresponds to virtual address va. If alloc!=0,
// create any required page table pages.
static pte_t *
walkpgdir(pde_t *pgdir, const void *va, char* (*alloc)(void))
walkpgdir(pde_t *pgdir, const void *va, int alloc)
{
pde_t *pde;
pte_t *pgtab;
Expand All @@ -52,7 +52,7 @@ walkpgdir(pde_t *pgdir, const void *va, char* (*alloc)(void))
if(*pde & PTE_P){
pgtab = (pte_t*)p2v(PTE_ADDR(*pde));
} else {
if(!alloc || (pgtab = (pte_t*)alloc()) == 0)
if(!alloc || (pgtab = (pte_t*)kalloc()) == 0)
return 0;
// Make sure all those PTE_P bits are zero.
memset(pgtab, 0, PGSIZE);
Expand All @@ -68,16 +68,15 @@ walkpgdir(pde_t *pgdir, const void *va, char* (*alloc)(void))
// physical addresses starting at pa. va and size might not
// be page-aligned.
static int
mappages(pde_t *pgdir, void *va, uint size, uint pa,
int perm, char* (*alloc)(void))
mappages(pde_t *pgdir, void *va, uint size, uint pa, int perm)
{
char *a, *last;
pte_t *pte;

a = (char*)PGROUNDDOWN((uint)va);
last = (char*)PGROUNDDOWN(((uint)va) + size - 1);
for(;;){
if((pte = walkpgdir(pgdir, a, alloc)) == 0)
if((pte = walkpgdir(pgdir, a, 1)) == 0)
return -1;
if(*pte & PTE_P)
panic("remap");
Expand Down Expand Up @@ -127,19 +126,19 @@ static struct kmap {

// Set up kernel part of a page table.
pde_t*
setupkvm(char* (*alloc)(void))
setupkvm()
{
pde_t *pgdir;
struct kmap *k;

if((pgdir = (pde_t*)alloc()) == 0)
if((pgdir = (pde_t*)kalloc()) == 0)
return 0;
memset(pgdir, 0, PGSIZE);
if (p2v(PHYSTOP) > (void*)DEVSPACE)
panic("PHYSTOP too high");
for(k = kmap; k < &kmap[NELEM(kmap)]; k++)
if(mappages(pgdir, k->virt, k->phys_end - k->phys_start,
(uint)k->phys_start, k->perm, alloc) < 0)
(uint)k->phys_start, k->perm) < 0)
return 0;
return pgdir;
}
Expand All @@ -149,7 +148,7 @@ setupkvm(char* (*alloc)(void))
void
kvmalloc(void)
{
kpgdir = setupkvm(enter_alloc);
kpgdir = setupkvm();
switchkvm();
}

Expand Down Expand Up @@ -188,7 +187,7 @@ inituvm(pde_t *pgdir, char *init, uint sz)
panic("inituvm: more than a page");
mem = kalloc();
memset(mem, 0, PGSIZE);
mappages(pgdir, 0, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc);
mappages(pgdir, 0, PGSIZE, v2p(mem), PTE_W|PTE_U);
memmove(mem, init, sz);
}

Expand Down Expand Up @@ -238,7 +237,7 @@ allocuvm(pde_t *pgdir, uint oldsz, uint newsz)
return 0;
}
memset(mem, 0, PGSIZE);
mappages(pgdir, (char*)a, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc);
mappages(pgdir, (char*)a, PGSIZE, v2p(mem), PTE_W|PTE_U);
}
return newsz;
}
Expand Down Expand Up @@ -315,7 +314,7 @@ copyuvm(pde_t *pgdir, uint sz)
uint pa, i;
char *mem;

if((d = setupkvm(kalloc)) == 0)
if((d = setupkvm()) == 0)
return 0;
for(i = 0; i < sz; i += PGSIZE){
if((pte = walkpgdir(pgdir, (void *) i, 0)) == 0)
Expand All @@ -326,7 +325,7 @@ copyuvm(pde_t *pgdir, uint sz)
if((mem = kalloc()) == 0)
goto bad;
memmove(mem, (char*)p2v(pa), PGSIZE);
if(mappages(d, (void*)i, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc) < 0)
if(mappages(d, (void*)i, PGSIZE, v2p(mem), PTE_W|PTE_U) < 0)
goto bad;
}
return d;
Expand Down

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